Oracle Message PLS-00455 - cursor string cannot be used in dynamic SQL OPEN statement

ERRORcursor string cannot be used in dynamic SQL OPEN statement
CAUSEdynamicly OPEN a REF CURSOR that has RETURN type. However, only REF CURSOR without RETURN type can be OPENed by an embebded dynamic OPEN statement.
ACTIONdefine a REF CURSOR without return type, and use it in the statement.